Why is 1+1 not 2 in HD?

[alegator]

The other day I was cutting a large DV-AVI file (captured from a Hi8 camcorder) into many parts using Adobe Premiere to burn them into DVD5's and the sum of the parts was exactly equal to the size of the original file as it should be. (For example a 7Gb file split into two 4.37Gb+2.63Gb files).
Now, I was trying to do the same for a large mpeg HD file (captured from my Sony HC-3 camcorder) and since Adobe Premiere CS4 does not recognize the file I tried both VideoReDo and Womble MPEG Video Wizard to do the job. The problem is that no matter how precise I set everything to perform the trimming the resulting files do not add up in size to the original source file, they always add a few bytes less. I wonder why is this happening, since there is no reencoding, I set everything to preserve the original format. Any clue? Thanks.

[Vidd]

There is overhead in a muxed mpeg file. It is common to have different file sizes depending what program is used.

It is possible you had a few frames corrupt and VideoRedo or Womble either dropped the frames or repaired the stream.

Also, the start frame must be an I frame and the last frame must be I or P. Otherwise the beginning or ending must be reencoded.

[poisondeathray]

Now, I was trying to do the same for a large mpeg HD file (captured from my Sony HC-3 camcorder) and since Adobe Premiere CS4 does not recognize the file

Isn't that an HDV camcorder ? Adobe Premiere CS4 should import HDV without any issue

[alegator]

Now, I was trying to do the same for a large mpeg HD file (captured from my Sony HC-3 camcorder) and since Adobe Premiere CS4 does not recognize the file

Isn't that an HDV camcorder ? Adobe Premiere CS4 should import HDV without any issue

Yes, Premiere is able to import it, but for some reason for this file which I'm not sure if it was imported with Premiere, Premiere pops a message that it lacks file support , so even though it shows in the Project media window, the source monitor displays the message of no support, so I'm unable to process/edit the file with Premiere.